Integrated circuit package with bond wires at the corners of an integrated circuit

ABSTRACT

An integrated circuit package which has an integrated circuit mounted to a substrate. The package includes a plurality of bond wires that couple bond pads of the integrated circuit to corresponding bond pads of the substrate. The bond wires may have an essentially uniform bond wire density about an entire outer perimeter of the integrated circuit including the corners of the circuit. The integrated circuit and bond wires are enclosed by an injected molded plastic housing. It is believed that the bond wires located at the corners impede the flow of the injected plastic and reduce the amount of wire sweep in the package from packages in the prior art. Additionally, the essentially uniform bond wire density may create a uniform fluidic resistance to the injected plastic. The uniform resistance also reduces the amount of wire sweep from packages in the prior art. The bond wires located at the corners may be dummy wires that are not electrically connected to the integrated circuit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an integrated circuit package.

[0003] 2. Background Information

[0004] Integrated circuits are typically assembled into a package thatis soldered to a printed circuit board. There are many types ofintegrated circuit packages including ball grid array (BGA) packages.BGA packages include a plurality of solder balls that are attached to asubstrate. The solder balls are eventually reflowed to mount the packageto a printed circuit board.

[0005] An integrated circuit is mounted to the BGA package substrate andtypically wire bonded to bond pads of the substrate. The bondedintegrated circuit and substrate are then placed into a mold that isinjected with a plastic material. The injected plastic encloses both theintegrated circuit and the bond wires.

[0006]FIG. 1 shows a typical wire bonded BGA package which has a numberof wire bonds 1 that couple an integrated circuit 2 to a substrate 3before the injection of plastic. The plastic is typically introducedthrough a gate at the corner(s) of the integrated circuit. The plasticis injected into the mold at very high pressures to insure that theintegrated circuit is completely encapsulated.

[0007] As shown in FIG. 2, it has been found that the injected plastic 4creates a “wire sweep” in the bond wires 1. A significant wire sweep canbreak the bond wires and create a defective part. It would be desirableto provide an injection molded wire bonded package that is lesssusceptible to wire sweep than packages in the prior art.

SUMMARY OF THE INVENTION

[0008] An integrated circuit package which has an integrated circuitmounted to a substrate. The package includes a plurality of bond wiresthat couple bond pads of the integrated circuit to corresponding bondpads of the substrate. The bond wires may have an essentially uniformbond wire density about an entire outer perimeter of the integratedcircuit. The integrated circuit and bond wires are enclosed by ahousing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a top view of an integrated circuit package of the priorart;

[0010]FIG. 2 is a sectional view of the integrated circuit package ofFIG. 1 with a housing that encloses an integrated circuit and aplurality of bond wires of the package;

[0011]FIG. 3 is a top view of an embodiment of an integrated circuitpackage of the present invention;

[0012]FIG. 4 is a side view of the integrated circuit package of FIG. 3;

[0013]FIG. 5 is a top view of a subassembled integrated circuit packagewithin a mold that is being injected with a plastic material;

[0014]FIG. 6 is a top view of an integrated circuit package with analternate bond wire pattern.

DETAILED DESCRIPTION OF THE INVENTION

[0015] One embodiment of the present invention is an integrated circuitpackage which has an integrated circuit mounted to a substrate. Thepackage includes a plurality of bond wires that couple bond pads of theintegrated circuit to corresponding bond pads of the substrate. The bondwires may have an essentially uniform bond wire density about an entireouter perimeter of the integrated circuit including the corners of thecircuit. The integrated circuit and bond wires are enclosed by aninjected molded plastic housing.

[0016] It is believed that the bond wires located at the corners of theintegrated circuit impede the flow of the injected plastic and reducethe amount of wire sweep in the package from packages in the prior art.Additionally, the essentially uniform bond wire density may create auniform fluidic resistance to the injected plastic. The uniformresistance also reduces the amount of wire sweep from packages in theprior art. The bond wires located at the corners may be dummy wires thatare not electrically connected to the integrated circuit.

[0017] Referring to the drawings more particularly by reference numbers,FIGS. 3 and 4 show one embodiment of an integrated circuit package 10 ofthe present invention. The package 10 includes a substrate 12 which hasa first surface 14 and an opposite second surface 16. The package 10 mayhave a plurality of solder balls 18 that are attached to a number ofcorresponding contact pads 20 of the substrate 12. The solder balls 18can be reflowed to attach the package to a printed circuit board (notshown). Although solder balls 18 are shown and described, it is to beunderstood that the package 10 may have other types of contacts such aspins which extend from the second surface 16 of the substrate 12.

[0018] An integrated circuit 22 is mounted to the first surface 14 ofthe substrate 12. The integrated circuit 22 may have a plurality of bondpads 24 that extend about the outer perimeter of the circuit 22. Thefirst surface 14 of the substrate 12 may also have a plurality of bondpads 26 arranged in a pattern about the integrated circuit 22. The bondpads 26 are coupled to the contact pads 20 by vias 27 that extendthrough the substrate 12.

[0019] The package 10 includes a plurality of bond wires 28 that couplethe bond pads 24 of the integrated circuit 22 to the bond pads 26 of thesubstrate 12. The integrated circuit 22 and bond wires 28 are enclosedby a housing 30. The housing 30 is typically constructed from aninjected molded plastic material.

[0020] In one embodiment, there is an essentially uniform bond wiredensity about the integrated circuit. The bond wire density may bedefined as the number of wires per cubic millimeters. The bond pads 26and/or 24 and corresponding bond wires located at the corners of theintegrated circuit 22 may be “dummy” wires that are not electricallyconnected to the circuit 22. The dummy wires are primarily provided toimpede the flow of the injected plastic material that forms the housing30 and to minimize the amount of wire sweep in the package 10.Alternatively, the corner wires may be dedicated to electrical power orelectrical ground.

[0021] To assemble the package 10, the integrated circuit 22 is mountedto the substrate 12 and wire bonded to the bond pads 26. As shown inFIG. 5, the substrate 12 and wire bonded integrated circuit 22 areplaced within a mold 32 that has a gate 34. Plastic material 35 isinjected through the gate 34 and into the mold 32. It is believed thatthe bond wires 28 impede the flow of the plastic and reduce the amountof wire sweep over packages in the prior art.

[0022] The plastic 35 is injected until the integrated circuit 22 andbond wires 28 are completely encapsulated. After the plastic hardens thesubstrate 12 and plastic enclosed integrated circuit are removed fromthe mold 32. The solder balls 18 are then attached to the substrate 12.The solder balls 18 are eventually reflowed to attach the package 10 toa printed circuit board.

[0023] While certain exemplary embodiments have been described and shownin the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not restrictive on the broadinvention, and that this invention not be limited to the specificconstructions and arrangements shown and described, since various othermodifications may occur to those ordinarily skilled in the art. Forexample, as shown in FIG. 6, the bond wires 28 located at the corner ofthe integrated circuit 22 may of a higher density and more closelyspaced together than the wires 28 at the other portions of the circuit22. For example, each corner may have two or more bond wires 28. Thenumber, spacing and density of bond wires 28 can be selected to controlthe fluidic resistance within the mold 32 and the wire sweep of thepackage 10.

What is claimed is:
 1. An integrated circuit package, comprising: asubstrate which has a plurality of bond pads; an integrated circuit thatis mounted to said substrate, said integrated circuit having a pluralityof bond pads that extend about an outer perimeter of said integratedcircuit; a plurality of bond wires that couple said bond pads of saidsubstrate to said bond pads of said integrated circuit, said bond wireshaving an essentially uniform bond wire density about said outerperimeter of said integrated circuit; and, a housing that encloses saidintegrated circuit and said bond wires.
 2. The integrated circuitpackage as recited in claim 1, wherein said housing is constructed froman injected molded plastic.
 3. The integrated circuit package as recitedin claim 1, further comprising a plurality of solder balls that areattached to said substrate.
 4. An integrated circuit package,comprising: a substrate which has a plurality of bond pads; anintegrated circuit that is mounted to said substrate, said integratedcircuit having a plurality of corners and a plurality of bond pads thatextend about an outer perimeter of said integrated circuit; a pluralityof bond wires that couple said bond pads of said substrate to said bondpads of said integrated circuit, at least two bond wires being locatedat said corners of said integrated circuit; and, a housing that enclosessaid integrated circuit and said bond wires.
 5. The integrated circuitpackage as recited in claim 4, wherein said bond wires located at saidcorners are not electrically coupled to said bond pads.
 6. Theintegrated circuit package as recited in claim 4, wherein said housingis constructed from an injected molded plastic.
 7. The integratedcircuit package as recited in claim 4, further comprising a plurality ofsolder balls that are attached to said substrate.
 8. A method forassembling an integrated circuit package, comprising: a) mounting anintegrated circuit to a substrate, wherein said integrated circuit has aplurality of corners; b) attaching a plurality of bond wires to saidintegrated circuit and said substrate including said corners of saidintegrated circuit; c) placing said integrated circuit, said substrateand said bond wires in a mold; and, d) injecting a plastic material intosaid mold to form a housing that encloses said integrated circuit andsaid bond wires.
 9. The method as recited in claim 8, further comprisingthe step of attaching a plurality of solder balls to said substrate.